High Energy Astrophysics of Compact Objects: Neutron stars, pulsars, and black holes.

Department of Physics
The George Washington University

We look at many different aspects of astrophysical compact objects (neutron stars, pulsars, black holes) to answer fundamental questions not only about these bizarre objects but also about related physical processes such as cosmic ray production, particle acceleration, compact binary physics, accretion, and supernova remnant (SNR) evolution. We also to study the entire population of Galactic X-ray sources (including black holes, microquasars, X-ray binaries).

Neutron stars are collapsed stars whose surfaces can be hot enough to emit radiation in ultraviolet and X-rays. In addition many neutron stars manifest themselves as pulsars - objects that emit short intense bursts of radio waves, x-rays, or visible electromagnetic radiation at regular intervals. Due to the extreme conditions in the neutron star interiors, these objects can be used as natural laboratories for studying the poorly understood properties of the superdense, strongly magnetized, superconducting matter. Such conditions can never be reproduced in Earth laboratories and therefore studying neutron stars provides the only way to learn about the nuclear reactions and interactions of the elementary particles under these extreme conditions. This information is of fundamental importance for particle and quantum field physics. Studying pulsar winds allows one to understand the complicated PWN morphologies, elucidate the dynamics of relativistic magnetized outflows and their interaction with the ambient medium (e.g., host SNR), and learn about particle acceleration in magnetized relativistic plasmas. X-ray and optical observations of neutron stars provide valuable diagnostics of all these processes.

Microquasars are the most extreme manifestations of stellar black holes. In these system (which are in many respects analogues to their supermassive counterparts in active galactic nuclei) matter pulled from a massive companion star falls into a black hole or onto a neutron star. In this proccess the matter heats up to very high temperatures and emits intense X-ray radiation. Due to the rapid rotation of the compact object s fraction of infalling matter is being ejected from the system along the compact object spin axis leading to formation of jets whose nonthermal emission can be seen througout a wide range of frequencies. Some microquasars are also emit very high energy (VHE) radiation in GeV and TeV bands. The exact mechanism responsible for the VHE radiation is has not yet been established with several possibilitites being currently explored.

Also learn about ghostly supernova remnants, another product of cosmic explosions!

Research Areas in Compact Object Astrohpysics:

Graduate students and postdocs trained in my group (more recent first):

Present and former collaborators (more recent first, the list is always incomplete):

Our group also includes several graduate and undergradue students working on various projects at George Washington University and Penn State University. We welcome new students and postdocs willing to work with us in these exiting areas of High-Energy Astrophysics! Our research is supported by vigorous observing program carried out on nearly all major space observatories (Chandra, XMM-Newton, Suzaku, HST, Spitzer) as well as Gran Telescopio CANARIAS (Spain), Very Large Array (New Mexico, US), and Australia Telescope Compact Array. Dr. Kargaltsev is also an associate member of VERITAS collaboration.

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Recent Developments and Selected Publications